In a contemporary compact disk (CD) system, a photodiode senses light transmitted to a disk by an optical pickup and converts the sensed, reflected optical signal into an analog RF signal. The analog RF signal output of the photodiode is provided to a data slice unit, where asymmetry in the signal is corrected. The asymmetry-corrected signal is provided to a peak detector, where it is converted into a rectangular signal on the basis of a predetermined bias level. An edge detector detects edges in the rectangular signal, and outputs pulses generated at the detected edges to an eight-to-fourteen demodulator (EFDM). The EFDM receives, in units of 14 bits, the pulse train generated at the detected edges, converts each 14-bit signal into an 8-bit signal, and outputs the converted 8-bit signal to an error corrector.
With ever-increasing optical disk recording density, digital video disk (DVD) systems have recently appeared. A DVD system recovers data from an analog RF signal for the EFDM, in a manner similar to the aforementioned CD system. However, data recorded at such high density must be recovered digitally, to minimize data loss, since analog recovery is unsuitable for adaptive recovery of data for the EFDM, due to variances in the type of optical disk and differences in manufacturing processes. Additionally, with an increase in demand for high-speed transmission and high density recording, when data is recovered according to the analog technique, data quality is adversely affected due to interference between signals.